This invention relates to a system for monitoring rotating equipment from a central station for the early detection of faults utilizing a self-contained and self-powered monitor located on each piece of equipment.
The need for techniques to monitor the performance of roller element bearings and detect their incipient failure has long been recognized. Several devices are known which measure the vibration emanating from a bearing and extract from the signal discriminants indicative of pending failure. One such device is the crest factor bearing monitor in U.S. Pat. No. 3,677,072 to B. Weichbrodt and B. Darrel granted on July 18, 1972. The sensitivity of this unit has been demonstrated in several successful applications, but the relatively high cost of building the device with meter relay and alarm limits its application to (a) dedicated installations on large, expensive, critical machines such as jet engines or (b) situations in which a large number of bearing installations can be periodically checked by service personnel with one or a few bearing monitors, such as production machinery in factories.
The advent of large scale integration (LSI) technology for manufacturing integrated circuits alters the situation drastically. The per unit cost of the crest factor bearing monitor is relatively low if volume production is assumed. Under this circumstance, dedicated installations can be justified in places where only periodic inspection could be considered in the past.
There remain certain implementation problems which must be addressed, however. Consider a large existing facility having a thousand or more bearing installations, specific examples of which are large power generating stations and chemical processing plants. It is feasible to provide an integrated circuit bearing monitor for each bearing. The monitoring system problems are principally supplying power to each bearing monitor and causing the output of the device to alert plant personnel to the bearing malfunction. Relative to the first, consider that in many applications, such as large motors and pumps, the only power available nearby is the high voltage/high amperage supply bus, and to tap off this is not a realistic solution. To signal a bearing defect to operating personnel, obvious possibilities are to activate an audible or visible indication of the bearing location or, via hardware, activate an alarm indicator in the plant's central control room. The problem with the former is that machines containing bearings may be unattended for long periods, and with the latter that this makes installation too expensive especially in a plant covering many acres.